Electromagnetic Waves

1. Electromagnetic Waves Chapter 13

2. Section 1: What are E-Waves? • Electromagnetic Waves are made by vibrating electric charges and can travel through space

3. Electric and Magnetic Fields • They are related forces that operate even in empty space. • A moving electric charge creates a magnetic field.

4. EM-wave Production • EM waves are produced when an electric charge is vibrating. • Vibrating charges are surrounded by vibrating magnetic and electric fields. • These fields travel outward from the moving charge

5. EM field - Properties • They carry radiant energy • As frequency increases; wavelength decreases. • Frequency is number of vibrations per second.

6. EM – Wave Speed • Wave speed – in a vacuum of space; is 300,000 km/s • EM waves slow as they travel through matter.

7. Waves and Particles • Differences between the two are not clear • Light can behave as a particle called a photon, whose energy depends on frequency. • All particles can behave like a wave.

8. Section 2: Electromagnetic Spectrum • The entire range of the electromagnetic wave frequencies is called the EM-Spectrum.

10. The EM Spectrum is arranged by the frequency of the wave. • Radio waves have the smallest frequency and longest wavelength. • Gamma rays have the largest frequency and shortest wavelength.

11. Radio Waves • Low-frequency • Wavelength less than 1 centimeter to about 1000 meters a. Microwaves- radio wave length about 1 to 10 cm

12. Radio Waves-Continued b. Radar-Radio waves bounced off an object to determine its speed and location. • c. Magnetic Resonance Imaging – (MRI) radio waves produce an image of the inside of the body.

14. Infrared Waves • EM waves with a slightly higher frequency than radio waves; people feel as thermal energy or warmth.

15. Visible Light • Has wavelengths between about 390 to 770 billionth of a meter, can be seen with the eye.

16. Visible Light Color • Red- smallest frequency, longest wavelength • Orange • Yellow • Green • Blue • Indigo • Violet- largest frequency, shortest wavelength

19. Ultraviolet Waves • Have frequencies slightly higher than visible light; can damage skin.

20. Ultraviolet waves-continued • 1. Ultraviolet light can kill bacteria • 2. Ultraviolet light can be absorbed by some fluorescent materials and released into visible light. • 3. Ozone layer absorbs most harmful UV waves.

22. X-rays and Gamma Rays • Ultra-high-frequency EM waves that can travel through matter, break molecular bonds, and damage cells.

25. Continued • X-rays are used to show images bones and to examine suitcases at airports. • Radiation therapy is used to kill diseased cells.

26. Section 3: Radio Communication

27. Radio Transmission • A radio converts EM waves into sound waves. • Carrier wave is the specific frequency of the radio wave to which a radio station is assigned

28. Radio Transmission • AM radio stations broadcast signals by varying amplitude of the carrier wave. • FM radio stations broadcast signals by varying frequency of the carrier wave.

29. Television • Sounds and images changed into electronic signals broadcast by carrier waves

30. TV - Continued • Audio sent by FM radio waves • Video sent by AM radio waves • A sealed vacuum chamber called a cathode-ray tube has a screen that can turn electron beams into images.

31. Telephones • Microphone converts sound waves into electrical signals. • Cell phone – signal creates a radio wave that travel to and from a microwave tower. • Cordless phone – uses transceivers to send and receive radio signals.

32. GPS • Global Positioning System – system of satellites, ground stations, and receivers that provide information about someone’s location.